Several types of insulating systems exist. A first type comprises several thicknesses, the last of which consists of a cladding panel or “facing panel”. It is often difficult to make the various thicknesses of materials hold together, notably when they are glass fiber or foam layers. Moreover, when this stack is produced, its mechanical strength is usually insufficient for the attachment of other elements.
To solve this problem, acoustic systems have been proposed comprising two rigid facing panels between which an acoustic insulating material is placed. Such a system is, for example, described in document WO 2007/080335. However this solution has three main drawbacks: the rigidity provided by the second facing panel is not always sufficient to confer the rigidity required for the desired use. Moreover, these acoustic systems have insulation “gaps” at certain noise frequencies. Finally, the second facing panel does not significantly improve the absorption of the noise, unless very thick facings are chosen, which can be a disadvantage in terms of space requirement, weight and costs.
In order to improve the rigidity of the foregoing structures, a proposal has already been made, in document JP 10037341, to interpose between the two facing panels a meshed rigid structure arranged to keep the two facing panels apart from one another in a rigid manner and so that acoustic absorbent material can be inserted between the two facing panels and through the mesh structure. This mesh structure consists of two flat meshes each attached to a single facing panel and separated by corrugated connecting elements attached to the two flat meshes. This structure is made up of rigid metal rods and makes it possible to reduce the mechanical transmission between the absorbent material and the facing panels. The acoustic absorption is slightly improved but to the detriment of the weight of the insulation panel. Moreover, the acoustic absorption function is provided only by the material placed between the two facing panels and in the mesh structure, the use of such a material already being known for this function. Finally, rigidity is only slightly improved.